This invention relates to the field of feed control systems for fluids. More particularly this invention relates to a reciprocating infusion pump.
Infusion pumps find widespread use in the medical and research fields. Accurate and reproducible flow rates, compact size, and the ability to vary flow rates over a wide range are all very important considerations for such devices; and many of the prior art devices are deficient in one or more of these features.
Typical commercially available infusion pumps are electrically operated, and this is especially true for reciprocating infusion pumps. These pumps suffer from one or more of the deficiencies noted above; and in addition may be undesirable for use in operating rooms and other environments where oxygen is used because of fire and explosion hazards from electrical arcing. Another problem with reciprocal infusion pumps relates to the need to control the direction of fluid flow from a reservoir to the syringes and from the syringes to the patient. Positive control of flow direction has not ordinarily been available for infusion pump devices.
Many prior art hydraulic control devices of general industrial types have incorporated what is known as a hydro-check control feature. Such devices have a pair of actuating cylinders arranged either in tandem or in parallel, with a mechanical connection between the actuating element. One cylinder has hydraulic fluid on both sides of its piston, with a flow path between the opposite sides of the piston. The other cylinder has provisions for selective application of pneumatic pressure to one side or the other of its piston. In the parallel arrangement the piston rods are connected together by a link external of the cylinders; in the tandem or series arrangement the pistons are connected by an extended piston rod. In addition to being only single acting rather than reciprocating, the parallel arrangement experiences side loads, and the tandem arrangement has size problems.